The present invention relates to a semiconductor device, and more particularly to a semiconductor device using a material having a high dielectric constant.
With the progressive microminiaturization of components in semiconductor devices, of late it has been required that the gate of a transistor should be 0.15 xcexcm in length and the gate dielectric film, if formed by SiO2, for example, should be made as thin as 2 nm or less in thickness.
With dielectric films having such a thin thickness, a tunneling current that passes through them is so large as not to be negligible. A possible solution to this problem has been considered to increase the physical thickness of the dielectric film while maintaining the dielectric properties by using a dielectric material having a higher dielectric constant than that of SiO2. Materials regarded as candidates for the above-mentioned material with high dielectric constant are zirconium oxide or hafnium oxide as is described in the 2000, February issue (pp.93-106) of Nikkei Microdevices, for example. However, zirconium oxide or hafnium oxide forms a layer of reaction compound with a thickness of about 1.5 nm xcx9c2.5 nm at the interface with the silicon substrate as stated in the lecture papers (Lecture No. 6.1, pp.99-133, and Lecture No. 6.4, pp.145-148) of 1999 IEEE (THE INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS) INTERNATIONAL ELECTRON DEVICES MEETING, for example.
Such reaction compounds are likely to degrade electrical characteristics.
The present invention has as its object to prevent deterioration of the electrical characteristics and provide a semiconductor device with improved reliability.
After assiduous efforts made to obtain measures by which to make it harder for oxygen to diffuse from a dielectric film that includes zirconium oxide as the cheif component element, the inventors have found it effective to add hafnium or titanium to the zirconium oxide.
On the other hand, from arduous endeavor to obtain measures by which to make oxygen less likely to diffuse from a dielectric film that includes hafnium oxide as the chief component element, the inventors have found it effective to add titanium to the hafnium oxide.
Moreover, the inventors have found that electrode materials, which have little tendency to allow oxygen to diffuse at the interface with the dielectric film that includes zirconium oxide or hafnium oxide as the chief component element, are cobalt silicide and silicon.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred and alternate embodiments.